1. Field of the Invention
The present invention relates to a fluorescent lamp lighting apparatus provided with an initial illuminance correction control circuit, and a lighting control system.
2. Description of the Related Art
A fluorescent lamp has properties that brightness is maximum in a lighting initial stage and then brightness is reduced with elapse of a lighting time. Such properties can be expressed as a light beam reduction curve. On the contrary, as a lighting target space, it is generally desirable to always perform lighting with a fixed illuminance even if lighting is carried out by using a fluorescent lamp. Thus, a dimming ratio is set to a value which is as small as possible to allow dark lightning in accordance with a reduction in a light beam involved by elapse of a lighting time from a lighting initial stage of a fluorescent lamp, and this dimming ratio is gradually increased with elapse of the time. As a result, there has been adopted a technique which controls lighting in a lighting target space with a fixed illuminance until an end of life duration of the fluorescent lamp. Such lighting control is referred to as initial illuminance correction control.
As described in, e.g., Jpn. Pat. Appln. KOKAI Publication No. 64-089287, the initial illuminance correction control is adopted in a lighting control scheme which first collectively controls an entire lighting target space. In this lighting control scheme, a common control device is installed separately from a plurality of lighting equipments, and the respective lighting equipments are connected with each other through a dedicated signal line or a signal line which also serves as a power supply line. Further, in the above-described lighting control scheme, fluorescent lamps in a lighting target space are concurrently subjected to the initial illuminance correction control by using a timer incorporated in the control device and table data in such a manner that a dimming level for each preset lighting elapse time can be achieved.
Furthermore, as a fluorescent lamp lighting apparatus, there is one which enables dimming and lighting based on external control. Such an apparatus includes a dimming control circuit. When an external dimming signal is supplied to the dimming control circuit, the dimming control circuit controls a high-frequency lighting circuit in accordance with the external dimming signal to adjust a high-frequency output which is supplied to a fluorescent lamp, thereby effecting dimming.